A B S TR ACT: Weathering processes have been studied in a podzol profile developed on sand during a postglacial period of 9400 years. Due to disintegration of rock fragments, the particle-size distribution has changed markedly in the upper part of the profile, and minerals have been transferred from sand fractions to silt and clay fractions. The most important weathering processes are the total breakdown of trioctahedral chlorite and biotite, and the transformation of dioctahedral mica (muscovite-phengite) to a regularly interstratified mineral, and further to Al-vermiculite or smectite. By using quartz as an internal standard, the annual loss due to weathering was found to be 3.2 g/m 2. The release of elements due to silicate weathering was calculated from depletion curves, and the average annual release of Na + K + Mg + Ca for the postglacial period was 19 mEq/m 2.This study is part of the Norwegian Surface Water Acidification Programme (SWAP) and is a continuation of the weathering studies by Nybakken (1984). The purpose is to determine the most important weathering processes and weathering rates during postglacial time. These rates are required when studying the possible effects of acid precipitation on soils and run-off water, as well as in studies of elemental cycling, and retention and loss of nutrients in forest ecosystems. Important cations such as Mg, Ca, K and Na are derived mainly from two sources, precipitation and weathering.
STUDY AREAThe study area, the field station Nordmoen, is located within the Romerike groundwater reservoir which has an area >100 km 2 (Ostmo, 1976), -40 km NE of Oslo, Norway. The study was performed on several profiles from a flat glaciofluvial sand deposit. The surface has a slope <0-5% showing no signs of postglacial erosion, the sediments are -60 m deep, and the groundwater table fluctuates between 1 and 3 m below the level surface.Due to rapid isostatic uplift, precipitation could have infiltrated the soil and initiated weathering shortly after the ice retreated 9400 BP (S~rensen, 1983). During the postglacial period there have been changes in climate, and the present mean annual precipitation and annual standard air temperature are 850 mm and 4.3~ respectively. Today the dominant overstory vegetation is pure Norway spruce with a few scattered pines, and the understory vegetation is dominated by Vaccinium myrtillus. Iron or iron-humus podzols (Typic Udipsamment, USDA) have developed in the glaciofluvial sand, and the soil profiles show no sign of previous cultivation.9 1990 The Mineralogical Society
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.